1. Field of the Invention
This invention relates to methods for reducing microbial growth in processes for the preparation or production of heat sensitive materials. More particularly, it relates to the inhibition of microbial contamination in processes for the production of food materials. Most particularly, it relates to the nominally aseptic production of single-cell protein materials such as yeasts.
2. Description of the Prior Art
Processes for the preparation of heat sensitive materials such as foods and food ingredients are generally required to meet stringent standards for cleanliness. Oftentimes there is a particular portion or segment of the process which is most vulnerable to bacterial contamination and which must be continually cleaned to maintain the product within specifications. Such cleaning operations are often time-consuming and expensive.
For example, during the processing of torula yeasts produced by continuous fermentation, a continuous centrifugation step is employed to concentrate the yeast broth from the fermentor (approximately 4 wt. percent solids) to a yeast cream (approximately 15 wt. percent solids). The centrifuge and ancillary piping, pumps, etc. are most susceptible to contamination by microorganisms which can build up in the system. Because high temperatures will damage the yeast cell, process temperatures much above 50.degree. C., such as those employed for pasteurization, cannot be employed at this stage of the process. Therefore, contamination in this portion of the process necessitates the use of daily clean-up procedures as a preventative measure, which generally involves using alternate centrifuges such that one is in service while the other is being cleaned. It would be extremely desirable to avoid this cumbersome procedure altogether or at least reduce the rate of contamination and hence the frequency at which cleaning must be performed.
Accordingly, it is an object of this invention to provide a method for reducing the rate of growth in microorganisms which may proliferate as contaminants in such systems. This and other objects will become apparent from further reading of this specification.